HDR III Some Examples

High Dynamic Range (HDR) image processing continues to be popular, and for good reason. Done properly, and with an HDR appropriate scene, some really nice images result.

The problem is that even though the concept is easy enough to understand, the actual application takes skill and experience. This isn’t to say a relatively inexperienced photographer shouldn’t be attempting HDR images, far from it. The experience gained through the process is invaluable for many parts of your skill set building. What I will say, is that you should expect to spend a significant amount of time perfecting all the variables involved with the technique. This isn’t simply entering values. This is about nuances, experience, personal taste, and more.

A fairly new but promising photographer send in this result of HDR processing and tells me:

“Steve, it just doesn’t look right. What am I doing wrong?”

He sent in two examples. An exterior of the Sanctuary of Truth, and an interior of the same temple.

At first take it's an interesting image. Then you start to notice a color cast in the sky, darker areas along the roof line which could be better lit, and the strongly saturated base. It’s nice, it could be better.

Let’s talk about the conditions and setup for this image. I was with him when he captured the exterior set of images. More, because his camera malfunctioned I loaned him my own camera. I also provided the tripod, external shutter release, and talked him through the exposures. He pointed the camera and following my advice learned what to look for in an HDR friendly scene, and how to capture it for maximum effect.

When we left Bangkok for the day it was raining. He was hesitant, not sure if we’d drive all that way and come up with a rainy drab scene. I was a bit more optimistic. After all, I’d just written more than a few pieces on getting out there during rain storms and looking for that rare shot with the dark rain swollen clouds in the background, and the sky opening up providing a beautiful directional light. I had to be optimistic. Put up or shut up time.

Ok, I got lucky. A few minutes on site and we were presented with the most beautiful conditions. The best conditions I’d ever seen for photographing the Sanctuary of Truth in the few dozen times I’ve been here. I was really pumped about collecting some great images to work with.

Then the unthinkable happened. His camera broke. A Canon 40D. What are the odds? A few months old, the failure surprised both of us. What could I do? Yep, I loaned him my professional Canon DSLR telling him I had tons of shots of the SOT. That part was true. As he was shooting the SOT I was already asking him “be sure to send me a few sets of these so I can try processing them.. “ Life is like this sometimes.

When capturing images for a HDR shot you expose for a well exposed sky (usually the brightest part of the scene), and then while maintaining the same aperture you increase shutter speed thereby increasing the exposure on the darker areas of the frame. You do this in 2/3 to 1 stop increments. Depending on the apparent/real dynamic range of the scene you’ll need to capture 2 or more increments. 3 - 5 would be pretty average, 7 - 10 not unusual. You want to use the minimum number of exposures/increments necessary to capture the full dynamic range.

He sends me the above HDR processed images, and then uploads the five exposures he used to my FTP. Looking at the five exposures I could immediately see the image only needed three of the exposures, not five. This is one of the three unprocessed:

Looking at the above image I could see that we needed two other exposures to achieve the full dynamic range of the scene, and because of the orientation of the lens to the building we’d also need to correct for a fair amount of perspective distortion on top of corrections for lens distortions.

This is my workflow. If you’re familiar with the software used you’ll be able to follow along. If not, you’ll get an idea but you’ll really need some more prerequisite experience either through a lot of self-learning, or a single day workshop on just HDR images.

Tone mapping has no set rules or guidelines. The controls will react differently to each image depending on the captured scene. This is basically what the Photomatix tutorial says and this is correct. This is where you’ll need to put in your hours of processing practice time to get a good feel for how the controls react to the different types of images you capture.

When done tone mapping close the program and it will bring it back into Lightroom

The seven steps above simply process the raw images into a tone mapped HDR image. The image is far from complete if you want maximum effect. The next steps take place in Photoshop.

From inside Lightroom select the tone mapped HDR image and export it into Photoshop.

Under the “Filters” menu select “distort” and then “lens correction.” Correct the lens distortion.

It still will look off, so now go to “Edit” and use the “Transform” tool to ‘skew’ the image the best you can. These last two steps take a considerable amount of experience so except to spend some time putting in the practice.

Now go to “Images” and choose “Levels” and adjust the levels for maximum effect. This will depend much on personal taste, but you don’t want to clip any highlights or shadows. Take your time on this and make sure you understand exactly what is happening to the image with each slight adjustment. It is easy to miss things here.

Now, go to “Image” and then “saturation” and adjust your final saturation levels in your color channels. Depending on what settings you chose in Photomatix a little to a lot of correction will be necessary.

Zoom in and check your noise levels. If necessary run the image through your noise reduction plug-in.

“Save” back into Lightroom. You are now ready to export a finished image in any size or image type desired.

Easy right? I’ve tried to cover HDR processing in single day workshops when we’ve already been going strong for 10-12 hours. In such cases it’s only possible to barely touch the surface of the basics. To learn HDR processing correctly, even at a basic level, it would take a full day. But at the end of the day you’d be able to process the image like this:

Pretty cool, eh? Dramatic but no overdone. Much but not all of the perspective distortion is corrected. The stormy dark clouds provide an excellent backdrop, and the temple itself is well exposed but not too much so. Much of this is taste, but this is how I did it.

Could you do close to this good without HDR processing? Sure, but the final result will take 2-3 times more skill and time in Photoshop.. and IMO won’t be as good. It certainly will not stand up to the close scrutiny of a large enlargement. This is what you could expect with a single exposure with the same scene.

It’s still not a bad image. The distortion was done a bit differently. It looks okay at this size, but loses a lot the closer you look.

Okay, now let’s look at the second image of the interior. Before we go any further I have to admit that I was knackered from the heat and was still recovering from being sick, by the time we wanted to do the interior. Instead of going in I retreated back to my SUV to rest in the blessed air-conditioning, but not before explaining how he needed to capture the scenes. Unfortunately I really should have gone in, because the scenes captures weren’t suitable to HDR.

Let’s take a look at the best exposed interior capture.

It looks fine as is, but as I looked at the set of five images I immediately noticed that five images were not enough. The inside was so dark, and the outside so bright, that perhaps as many as 11-13 increments/images were necessary. This would be easy enough to check using the LCD and zooming in on the windows to check exposure, but I failed to mention this finer point before he went in.

The result was all five images had severely overexposed highlights outside the windows. Because the lens being used was a fast 20mm F1.8 lens used at F2.8 (as I suggested), chromatic aberrations manifested in a huge way. Take a look.

See the purple and blue lines running along the vertical and horizontals? This is CA. Usually you can easily remove mild to moderate CA in you raw converter such as Lightroom or ACR. This was so bad it couldn’t be removed.

I went ahead and HDR processed the five images anyway, knowing full well the images would be unacceptable because of the CA. But I processed them so you could get an idea of what HDR would offer in such a scene had we properly captured it in the first place.

Now, imagine this image with blue or cloudy skies showing in the blown out highlighted areas. This would have made an awesome capture! See the directional light on one side of the pillars? The reflections in the floor? Exposure detail in the roof and walls? He was soooo close to perfection.

HDR is like that. You either nail it perfectly, or you don’t.

I hope this helps those of you still working on your HDR techniques gain a little more perspective into the capture and processing of HDR images.